How do we make sense of the drug trade from a sociological and historical perspective?

I and, I assume, most other Flutherites, are shielded from the direct consequences of the drug trade, but the stories I hear on the news are rather hair raising. There are neighborhoods in the U.S. where people do not go out at night for fear of getting caught up in fights between rival drug gangs. Drug cartels in Mexico and Colombia act at a national level. There are terrorist organizations funded by drug sales.

I know people have used drugs throughout history, but I do not recall reading about conditions anywhere close to those of recent times. Is drug use higher now than in the past? Has drug traffic been influenced by chemical processing that makes drugs more potent? Who are the primary drug users? Is it mainly people in industrialized nations? Is it mainly used by the poor? Is it only in recent times that drug use has been made illegal and, if so, what
would be the consequences of making drugs legal?

I really do not understand what is going on and would appreciate any light that can be shed on the situation.